This invention relates in general to mills for rolling metal products such as strands, strips, wires and profiles. More specifically, it relates to a cantilever apparatus of compact size for rolling a metallic material and a method of producing a metallic product.
Rolling mills are used for reducing the thickness and shaping of metallic products. There are two kinds of rolling mills. First there are rolling mills where work rolls have strong supportive bearings connecting the work rolls to the mill frame at both ends of the work rolls and the mill frame is covering the whole rolling mill. These are called “normal” rolling mills. The other kind of mills are called cantilever rolling mills, where the actual rolling is done outside the mill frame and the work rings are assembled on roll shafts which are supported by the mill frame only from the other side of the nip. The term “nip” is used herein to refer to the region where the work rolls or rolling rings are closest together.
The high forces associated with the rolling are guided to the work roll bearings/roll shaft bearings, which therefore have to be strong, that is heavily build. The forces directed to the bearings are over two times higher in cantilever rolling mills than in “normal” rolling mills due the structural design of the cantilever mill. The rolling forces in cantilever rolling mills are mainly carried by the heavy main bearings and the smaller bearings at the drive end of the roll shafts are just countering the bending moment caused by the rolling force. Traditional cantilever rolling mills are described e.g. in U.S. Pat. No. 4,581,911 and U.S. Pat. No. 5,056,345. The higher rolling forces with cantilever rolling mills are leading to even bigger/stronger bearings and mill frame construction as with the “normal” rolling mill and are preventing the use of cantilever rolling mill in some occasions.
In U.S. Pat. No. 4,581,911 are described a cantilever type rolling mill having a pair of roll shafts rotably supported in a roll housing on a roll stand. The assembly is designed to transmit torque to a ring roll by frictional force produced by application of compressive force on the opposite lateral sides of the ring roll.
In U.S. Pat. No. 5,056,345 are described a rolling stand with rolling rings supported as cantilever and having their axes at an angle to each other for the rolling of metallic products. The angle between the axes of the shafts is to compensate the bending of the shafts during rolling produced by the high rolling force. This high rolling force and the bending of the shafts are requiring very massive bearings and mill frame for the rolling stand.
In U.S. Pat. No. 5,524,469 are described a cantilevered cluster mill stand assembly for rolling long products. A basic improvement to normal cluster mill stands is the mounting of the rolling bearings upon a stationary cantilevered arbor directly under the roll ring, eliminating heavily loaded main reaction bearings within the stand housing in limited radial space. Individual drive motor assemblies for each shaft, rigidly coupled and directly supported by the drive shafts, are also advocated. However, even in this solution the forces with the support rolls are quite high because the unsuitable angles with the transfer of the rolling forces to the support rolls.
Despite the stronger bearings and other described solutions the cantilever rolling mills are not capable to handle as high rolling forces as “normal” rolling mills. This limits the use of the cantilever mills seriously despite of the many benefits achieved with this mill construction over “normal” mill construction.